We are investigating the relationship between the antioxidant/pro-oxidant status of pigmented rats and their susceptibility to retinal degeneration as a function of light dose. We are studying the occurrence of antioxidant enzymes (glutathione peroxidase, peroxidase, catalase and superoxidase dismutase) in the retina, rod outer segments (ROS) and retinal pigment epithelium (RPE). The activities of anti-oxidant enzymes and the state of oxidation of the lipids in RCS rats will be measured. The major oxidation product of the ROS lipids will be identified and isolated. The changes in lipid microstructure will be studied with a fluorescent probe, parinaric acid. We are attempting to develop a functional assay for the disk membrane.